Frequently, coded information messages relating to the condition of memory means, measuring devices, and the like are transmitted by a line signal (e.g. via a telephone line) in one of two forms. When sequential point-to-point communication is conducted, a relatively long information signal sequence is transmitted. However, when a multi-point communication is conducted, generally a shorter information signal sequence is transmitted. The information sequence of the message is usually preceded by a preamble which is indicative of the presence of the forthcoming information sequence. A receive line signal detector first senses the preamble portion of the coded message to determine if it is above a given threshold level so as to be able to discriminate between the presence of information signals and noise. The receive line signal detector must be responsive to both long and short information sequences. When the amplitude of the coded message drops below a lower level for a particular interval of time, the information sequence is assumed to be completed. After this particular time interval, the receive line signal detector indicates that the information sequence is absent.
This invention relates to a unique, compact, power saving averaging and peak detection circuit to function in either of a relatively slow charging, signal averaging mode or a relatively fast charging, signal peak detection mode of operation so as to be responsive to both long and short information messages, while having a relatively slow discharge time in either mode.
Examples of prior art circuits are included in the following patents:
U.S. Pat. No. 3,307,048 Feb. 28, 1967
U.S. Pat. No. 3,469,111 Sept. 23, 1969
U.S. Pat. No. 3,596,109 July 27, 1971